1. Field of the Invention
This specification relates to a three-phase power line communication apparatus and a communication method thereof, and more particularly, to a three-phase power line communication apparatus capable of establishing a network group for each of three phases, and capable of performing communication according to the established network group, and a communication method thereof.
2. Background of the Invention
FIG. 1 is a conceptual view illustrating a configuration and an operation of a remote reading system in accordance with the conventional art.
As shown in FIG. 1, in the conventional remote reading system, when meters of modems for three phases perform meter-reading communication with a master device having a three-phase communication modem, the lower meters connected to each phase are recognized as a single network. Then, the meters are selected by ID order or arbitrarily, and reading data is requested. When meter-reading communication fails, re-transmission of the reading data is requested by applying the same policy to all the meters.
The conventional remote reading system does not consider communication collision which may occur when an independent network of three phases is processed by a single apparatus. A single master device simultaneously requests data from a plurality of meters, so as to collect reading data of the plurality of meters.
A meter modem checks whether a channel is available before attempting to perform communication due to characteristics of power line communication (PLC). If the channel is in an available status, the meter modem starts communication by sending a signal indicating that the channel is in an available status. In this instance, a meter modem for S phase and a meter modem for T phase cannot receive the signal before meters for R phase attempt communication, because communication for three phases is performed in a separated manner by each phase. While a single meter for R phase attempts to perform communication, meters for S and T phases may perform communication. This may cause the master device which simultaneously receives signals for three phases, to have communication collision.
Further, a network for each phase requests re-transmission of data, if a response to a data request is not received from a plurality of meters. In this instance, each meter has a different communication performance. A meter having an excellent communication performance may have a small number of re-transmission, whereas a meter having a poor communication performance may have a large number of re-transmission. However, in the conventional remote reading system, the same number of re-transmission is performed without considering such a principle. As a result, a meter having a poor communication performance may not make reattempts, even in a situation where a preset number of times of re-transmission is 3 times, and the meter having a poor communication performance can succeed if it makes reattempts 4 times. This may cause failure of data transmission.